1. Field of the Invention
The present invention generally relates to military or ordnance articles and specifically to the production of fragmentation casings for hand grenades, weapon-launched grenades and other explosive ordnance articles of the type having a charge that is enclosed by a casing member and a delay or contact fuse for initiating the charge.
2. Description of the Prior Art
Various ordnance articles of the above mentioned type are known, e.g. grenades or mines for launching (by hand or by a weapon) or for installation in the soil and the like. The common feature of such articles, insofar as the invention is concerned, is a fragmentation casing, that is, a shell, wall or the like member intended to produce a fragmentation effect substantially due to preformed fragments, i.e. fragments formed into their final shape before detonation of the explosive charge.
In conventional hand grenades, for example, a steel casing made for instance by casting is furnished with an array of notches that more or less define the shapes of fragments of the casing resulting from disntegration thereof upon explosion of the charge. Such all-metal casings are quite heavy in relation to the number of fragments resulting from explosive disintegration; to reduce the weight of such casings and so simplify production thereof it is known in the art to form a composite casing on the basis of synthetic polymer compositions with preformed metal fragments embedded therein.
Typical hand grenade casings of this type are disclosed, for example, in U.S. Pat. No. 2,762,303, in French Pat. Nos. 1,237,195 and 2,142,270, in German patent application No. 1,164,883 and in Swiss Pat. Nos. 388,141 and 405,113.
For producing such casings various synthetic polymers or plastics constituents, both of the thermoplastic and duroplastic (thermosetting) type, have been suggested in the art together with various methods of shaping the casings, e.g. by casting, injection molding or press molding. For example, one prior art method provides for first forming two shells from polystyrene with metal particles embedded therein and adhesively combining such shells and finally surrounding the casing component obtained with a jacket of polyethylene by injection molding.
In practice, however, such prior art methods have not proved satisfactory, either because the metal fragments embedded in the plastics casing and penetrating through the casing result in an uncontrolled weakening of the material and/or because the proposed methods can only be carried out at considerable expense, if at all. Thus, for example, the method suggested in the above mentioned Swiss Pat. Nos. 388,141 and 405,113 provides for embedding the metal fragments in a shell of a first plastics material and subsequent injection molding of a second plastics material around this shell. However, the fragment-embedding shell must be relatively thick for subsequently encasing it by injection molding with a second casing so that the cavity volume becomes either too small or the casing too heavy. Furthermore, the method requires many manufacturing steps as well as expensive molds and equipment.
Accordingly, it is a main object of the invention to provide for a novel structure of a fragmentation casing in whichthe preformed metal fragments do not substantially weaken the plastics-based wall member of the casing.
A further object is a fragmentation casing which is an integral or monolithic structure having an outer layer of an organic polymer composition and an inner layer formed of metal fragments.
Yet another object of the invention is an improved method of making fragmentation casings by molding both the plastics-based wall member of the casing and the casing constituent that holds the preformed fragments in a single molding step.
Further objects will become apparent as the specification proceeds.